Resilient coupling

ABSTRACT

A coupling for two generally coaxially aligned shafts which comprises an annulus having a series of rectilinear, resilient, and compressible columns connected with their longitudinal axes along the sides of a flat polygon. Arms project transversely from the longitudinal axes at each intersection of two adjacent columns; the arms alternately project from the front and rear faces of each of the adjacent columns with respect to the plane of the flat polygon. Hubs are secured on each of the shafts for receiving the alternate arms on the annulus respectively; fasteners operate radially through each arm for securing the arms to the hubs and decreasing the radius of the annulus thereby placing the columns under a precompressive load. A recess is formed on each of the front and rear faces of each column extending from the projection of the arms toward the opposite end of each column for reducing axial thrust during compression of the annulus.

United States Patent [191 Calistrat [111 3,724,239 1 Apr.3,1973

[54] RESILIENT COUPLING [75] Inventor:

[73] Assignee: Koppers Company, Inc., Pittsburgh,

[22] Filed: Feb. 8, 1972 [21] Appl. No.: 224,505

Primary ExaminerCharles J. Myhre Assistant Examiner-Randall HealdAttorney-Boyce C. Dent et al.

Michael M. Calistrat, Baltimore,

[57] ABSTRACT A coupling for two generally coaxially aligned shaftswhich comprises an annulus having a series of rectilinear, resilient,and compressible columns connected with their longitudinal axes alongthe sides of a flat polygon. Arms project transversely from thelongitudinal axes at each intersection of two adjacent columns; the armsalternately project from the front and rear faces of each of theadjacent columns with respect to the plane of the flat polygon. Hubs aresecured on each of the shafts for receiving the alternate arms on vtheannulus respectively; fasteners operate radially through each arm forsecuring the arms to the hubs and decreasing the radius of the annulusthereby placing the columns under a precompressive load. A recess isformed on each of the front and rear faces of each column extending fromthe projection of the arms toward the opposite end of each column forreducing axial thrust during compression of the annulus.

30 Claims, 8 Drawing Figures PATENTEBAPR 3 1975 3 724 239 SHEET 1 OF 2PATENTEDAPRS 1975 3,724,239

sum 2 [IF 2 G g' 36 I8 34 64 [LL RESILIENT COUPLING CROSS-REFERENCESThis invention relates generally to co-pending design application Ser.No. 228,785, filed Feb. 23, 1972 (assigned to the assignee of thepresent invention and claiming the esthetic appearance of theelastomeric annulus disclosed herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to flexible shaft couplings utilizing a yieldingelement for transmitting rotary motion between two generally alignedshafts.

2. Description of the Prior Art Attempts have been made heretofore tomake flexible couplings from a non-metallic, resilient material, such asrubber, because of the advantages imparted to the couplings. Forexample, they require no lubrication; they are usually economical tomanufacture; and they are torsionally resilient. In most instances, theconnected equipment is subject to shock loads. The nature of thecoupling determines the extent to which the shock is transmitted fromone shaft to the other. Resilient couplings are especially attractivefor applications where a minimum transmission of the shock loads isdesired.

Couplings of such materials, however, have not been particularlysuccessful because of the disadvantages attendant with the use of theresilient material. Natural rubber, for example, has poor mechanicalproperties in tension; it tends to crack thereby exposing a greatersurface area to ozone attack. A synthetic rubber, such as neoprene orBuna N is not so subject to ozone attack. These synthetic rubbers,however, have mechanical properties that are poorer as far as couplingsare concerned than natural rubber, especially in those applicationswhere the coupling is subjected to stresses resulting from torsionalloads, and from axial and angular misalignment.

The foregoing disadvantages have been generally overcome by attaching aprecompressed elastomeric annulus between a pair of hubs mounted on apair of substantially coaxially aligned shafts. An example of this typecoupling is shown in Landon et al. U.S. Pat. No. 3,296,827.

However, it has been found in some instances that precompression of theelastomeric-annulus causes axial thrust forces to be created in theannulus which are transmitted through its connections to the shafts.Such axial thrust forces are generally undesirable where the shafts aremounted in bearings. Even at zero torque and zero misalignment the axialthrust forces may be extremely large and when imparted to the shaftswill cause unwanted stresses and forces on the shafts bearings, whichmay sometimes cause excessive bearing wear and shortened bearing life.

SUMMARY OF THE INVENTION Accordingly, an object of the present inventionis to provide a resilient coupling that will overcome the aforementioneddisadvantages and others. Thus, this invention provides for a flexiblecoupling which utilizes a resilient compressible material which ispreloaded in compression as disclosed in Landon et al. U.S. Pat. No.

3,296,827; and, in addition, this invention effectively reduces theaxial thrust forces inherent in the abovementioned type of coupling andothers.

This is generally accomplished by providing an annulus with a series ofrectilinear, resilient, and compressible columns connected with theirlongitudinal axes along the sides of a flat polygon. Arm means projecttransversely from the longitudinal axes at each intersection of twoadjacent columns. These arm means alternately project from the front andrear faces of each of the adjacent columns with respect to the plane ofthe flat polygon.

A hub means is provided on each of the shafts for receiving alternateones of the arm means respectively. A fastening mean is provided whichoperates radially through the arm means to the hub means for decreasingthe radius of the polygon thereby placing the columns under aprecompressive load.

The annulus is further provided with a recess on each of the front andrear faces of the columns. These recesses extend from the projection ofthe arm means toward the opposite end of the columns and affects thecharacteristics of the annulus in such a manner that the axial thrustforces created by precompression of the annulus are substantiallyreduced and sometimes eliminated entirely, at any torque level.

The above and further objects and novel features of the invention willappear more fully from the following detailed description when the sameis read in connection with the accompanying drawings. It is to beexpressly understood, however, that the drawings are not intended as adefinition of the invention but are for the purpose of illustrationonly.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts aremarked alike:

FIG. 1 is an exploded perspective view of the resilient coupling of thepresent invention;

FIG. 2 is an isometric view of an arm means of FIG.

FIG. 3 is a front elevational view of the annulus of FIG. 1 incross-section;

FIG. 4 is a detailed view of an arm means joint of FIG. 2;

FIG. 5 is a detailed view of the split arm means of FIG. 1;

FIG. 6 is a perspective view of a portion of the annulus of FIG. 1,showing two different configurations of the recesses;

FIG. 7 is a top plan view of the annulus of FIG. 1; and

FIG. 8 is a top plan view of another configuration of the annulus forthe resilient coupling of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 theinvention generally comprises a resilient coupling denoted generally bynumeral 10, for two generally coaxially aligned shafts 12 and 14. Thecoupling comprises an annulus 16 having a series of rectilinear,resilient, and compressible columns 18 connected with their longitudinalaxes 20, as shown in FIG. 3, along the sides of a flat polygon 22. Anarm 24 projects transversely from the longitudinal axes 20 at theintersection 26 of two adjacent columns 18. The arms 24 alternatelyproject from the front and rear faces of each of the adjacent columns 18with respect to the plane of the flat polygon 22. Hubs 28 and 30 aresecured on each of the shafts 12 and 14 for receiving the alternate arms24 on the annulus 16 respectively. Fasteners 32 operate radially througheach arm 24 for securing the arms 24 to the hubs 28 and 30 and fordecreasing the radius of the annulus 16 thereby placing the columns 18under a precompressive load. A recess 34, shown in FIGS. 1 and 7, isformed on each of the front and rear faces of each column 18 extendingfrom the projection of the arms 24 toward the opposite end 36 of eachcolumn 18 for reducing axial thrust forces created in the annulusbecause of compression of the annulus 16 during its assembly to hubs 28and 30 and remaining during precompression of the annulus.

More specifically, the present invention as shown in FIG. 1 comprises apair of generally axially aligned and substantially abutting shafts l2and 14 which are to be coupled in a torque transmitting relationship bythe resilient coupling denoted generally at 10. As illustrated herein,hubs 28 and 30 are mounted on shafts 12 and 14 and are to be joined byan annulus 16.

Hubs 28 and 30 may be secured to the shafts 12 and 14 in any suitablemanner, as by set screws 38 being placed through correspondinglythreaded apertures 40 in collars 42 formed on hubs 28 and 30, andtightened down on shafts 12 and 14, thus securing the hubs 28 and 30 toshafts l2 and 14. Hubs 28 and 30 have wedge shaped slots 44 in theirperimeter. These slots 44 are, in the embodiment shown, spaced equallyaround the hubs 28 and 30. Centrally located in each slot 44 is a'threaded aperture 46.

Adapted to fit in slot 44 are arms 24 that project from annulus 16.These arms 24 are wedge-shaped to conform to the shape of slots 44.These arms 24 also include an aperture 48 through which a fastener, suchas a cap screw 32, extends for threading into aperture 46 in hubs 28 and30. If desired, the aperture 48 may be counterbored as at 50 to receivethe head of cap screw 32.

As illustrated herein, the arms 24 and the annulus 16 are one integralunit. The arms 24 are preferably metallic such as aluminum and arepreferably molded in the annulus 16 as shown in FIG. 3 when the annulusis cast. This has the advantage that the resulting part is one piece, iseasily and cheaply made, and more importantly, it is readily handled andinstalled.

Arms 24 project, alternately, first from one side of the annulus 16 andthen from the other side. In the embodiment illustrated herein, fourarms 24 project in one direction from the front face of annulus 16 andfour arms 24 project from the rear face. The arms 24 on each face arepreferably spaced 90 apart so that the angle between adjacent arms 24 is45. These arms 24 serve to attach the annulus 16 in staggered fashion tothe hubs 28 and 30 on shafts l2 and 14. The distance or radius of thesearms 24 from the axis of annulus 16 in its free state is to percentgreater than the fixed distance or radius of slots 44 from the axis ofshafts 12 and 14. As arms 24 are fitted in the slots 44 of hubs 28 and30, they decrease the diameter of the annulus 16 and thus compress thematerial of annulus 16.

' The arms 24 are of a length sufficient to span the distance 52 acrossthe axial width of the annulus 16 and the axial width 54 of the slot 44in the hubs 28 and 30. v

The arms 24 are preferably made of aluminum for reasons of strength. Thealuminum arms 24 can be conveniently molded in the material from whichthe annulus 16 is made.

Annulus 16 is comprised of a series of rectilinear, resilient, andcompressible columns 18 connected with their longitudinal axis 20 on thesides of a regular polygon 22, as shown in FIG. 3. Still referring toFlG. 3, the arms 24 are positioned at the point of intersection 26 ofthe longitudinal axes 20 of two adjacent columns 18, such as 20!. and20R, and project transversely of the longitudinal axes 20 of the column18. Referring to FIG. 4, as a practical matter the midpoint 56 of arm24, is not the axis 20 of the two lines of intersection 58 of the axes20 of two adjacent columns 18 because the adjacent corners 60 arepreferably rounded to alleviate stresses. Accordingly, the center 56 ofthe arm 24 is positioned along the fillet radius 64 joining the axes 20of two adjacent columns 18.

The arms 24 are molded. within the longitudinal columns 18 and aresubstantially the same width as the cross-sectional area of the column18. It is preferred bond of the arm 24 in the annulus 16, shown in FIGS.2

and 3. The sides 62F and 62B of the arms 24 taper inwardly asillustrated by. the dotted lines F and B. The sides 62F and 62B of twocircumferentially adjacent arms 24 with one column 18 of the annulus l6therebetween forms a substantially rectangular section of the column 18.

Annulus 16 is made of a resilient material, preferably from materialsuch as rubber which is deformable under a compressive force. A plastic,such as'polyurethane may also be used if desired. The nature of theresilient, compressible material, of course, will vary with therequirements in operation.

Advantageously, the rubber from which the annulus 16 is made has a ShoreA durometer hardness of 55-65. If the material is too soft, it will, ofcourse,deform too much andif it is too hard, it will impose bearingloads on the shafts 28 and 30 that are intolerable.

A further feature of this invention, as shown in FIG. '5, is that one ofthe arms 24 may be split along a radially extending plane passingthrough the center of the arm 24. This permits the annulus 16 to bespread apart so that it may be installed around shafts 12 and 14 whenthey are very closely coupled without'the need for moving hubs 28 and30. Even when the shafts. 12 and 14 are not closely coupled, because ofthe nature of the coupling used, it had been necessary, heretofore, toback off the shaft in order to mount an annulus to the'coupling hubs 28and 30. The split annulus 16 of this invention overcomes the foregoingproblem as the annulus 16 can be opened tobe placed upon or removed froma shaft 12 or 14 or coupling unit 10. Another important feature of splitarm 24, is that the sides 25 and 27 on each side of split arm 24 aretapered inwardly to correspond to the tapered sides of slot 44 in hubs28 and 30. When annulus 16 is opened and placed around shafts 28 and 30,both ends of split arm 24 are then placed in one slot 44 and a cap screw32 is placed through aperture 48. As the cap screw 32 is tightened intoaperture 48, the tapered sides 25 and 27 of split arm 24 engage thetapered sides of slot 44 and; as the cap screw 32 is further tightened,the sides 29 and 31 are forced together 'by the wedging action createdas the split arm is forced radially inward by cap screw 32. This wedgingaction will ensure that the split arm is always secured in slot 44,eliminating the possibility of the split arm 24 separating at the joint.These features of the split annulus 16 enables the application of thecoupling under conditions where it had been necessary heretofore to backone shaft away from the other in order to install the coupling.

The above-mentioned coupling has successfully overcome theaforementioned disadvantages and others, but, in its present state, itstill contains an undesirable characteristic which, without beingeliminated, could cause excessive axial thrust forces on the shaftsbearings. It was found that the axial thrust forces that are created byplacing it in compression are transmitted from the annulus, through thearms, through the hubs, through the shafts, and to the shafts bearings.Even at zero torque, zero axial misalignments, and zero offsetmisalignments, these axial thrust forces are appreciable, which causeexcessive bearing wear and shortened the bearing life. These forces areunacceptable in many applications, but it has been discovered thatthrough a change in geometry of the flexible element, these forces canbe substantially reduced or even eliminated under conditions of no axialmisalignment.

Referring now to FIGS. 1 and 7, generally this change in geometrycomprises a recess 34 formed on each of the front and rear faces of eachcolumn 18 extending from the projection of the arms 24 toward theopposite end 36 of the columns 18. It was discovered that the additionof recesses 34 would effectively reduce the axial thrust forces aftercompression of the annulus 16.

More specifically, recess 34, as shown in FIG. 7, is wedge-shaped,tapering from its deepest point 64 adjacent the projection of the arms24 to the surface 36 of each of the front and rear faces of each column18. The length L of each recess 34 is a variable and may be less thanone-half the length LL of each column 18, or it may be more thanone-half the length LL of each column 18, or the length L may besubstantially equal to one-half the length LL of each column 18. Thedimensions of length L is based on that length which will produce theleast amount of axial thrust forces for the correct size andconfiguration of the coupling to be used. It has been discovered thatthe preferred length L g for most coupling applications is that lengthwhere the wedges are formed at substantially identical angles a on boththe front and rear faces of each column 18 and will provide each column18 with a substantially uniform cross-sectional area with respect to theflat sides of each column 18.

Referring now to the right hand portion of FIG. 6, a second type ofrecess may be formed which will also effectively reduce the axial thrustforces. This recess 34A is formed as a truncated wedge tapering from itsdeepest point 66 adjacent arm 24 to a point 68 below the surface 70 ofcolumn 1.8 and then rising at an angle E at point 68 to the surface 70.The preferred method of formingthe angles at points 66 and 68 is to formthem on a radius as shown, that is, a fillet radius, and not as a sharpangle as shown in FIG. 7 as point 64. It has been discovered that due tothe extreme forces exerted on the annulus 16 during operation, the pointat which the angle was formed would produce cracks in the annulus 16 ifthe angle was sharp, but forming the angles on a radius as shown in FIG.6 would eliminate any such cracking. As shown in the right side of FIG.6, the width W of the truncated wedge is less than the radial width WWof the front and rear faces of the column 18, thus the truncated wedgeis formed within the confines of the periphery of the front and rearfaces of each column 18 thereby forming walls 76 and 78 on each side ofthe truncated wedge. It is to be understood that the truncated wedgeneed not be formed within the confines of the periphery of the front andrear faces of each column 18, as shown, but may be formed at the topsurface 80 or the bottom surface 82 thereby forming only one wall 76 'or78 between the edge 84 of the truncated wedge and the edge 86 of thecolumn 18. The preferred method, is to have the width W of the truncatedwedge equal to the radial width WW of the front and rear faces of column18 thereby eliminating the side walls 76 and 78 such as shown for therecess 343 on the left side of FIG. 6. It isalso to be noted that theangles formed at points 66 and 68 are variable, and can vary from wherethe angles formed atpoints 66 and 68 are substantially right anglesthereby forming a recess 34 rectangular in shape, not shown, to wherethe angle formed at point 68 is zero, thereby forming a wedge-shapedrecess 34, as shown inFIG. 7.

The preferred configuration of the recess 34 is as shown in the lefthand portion of FIG. 6. Recess 34B is wedge-shaped as previouslydescribed, with the angle 88 formed on a radius and where the width W ofthe wedge is equal to the radial width WW of the front and rear faces ofcolumn 18. It has been found that, as a rule, for a rubber annulus witha Shore A durometer hardness of 55-65 a substantial reduction of theaxial thrust forces is accomplished if the angle a of the wedge is 6 andthe length L of the wedge is 55 percent of the length LL of the column18. These proportions are preferred for most applications althoughexperimentally, dimensions slightly different than the above can befound to provide zero axial thrust. It is to be understood that shouldan annulus be made with a Shore A durometer hardness different than thatmentioned above the dimensions of the wedge will also vary. For example,should the element have a Shore A durometer hardness of less than 55then the wedge will be formed witha smaller angle than 6 and a shorterlongitudinal length than 55 percent of the longitudinal length of thecolumn, and, should the element have a Shore A durometer hardness ofgreater than 65, then the wedge will be formed with a larger angle then6 and a longer longitudinal length than 55 percent of the longitudinallength of the column.

However, it is to be further understood that the width W of the wedgemay be less than the radial width WW of the front and rear faces ofcolumn 18 thereby forming at least one wall between the edge of thewedge and the edge of the column 18 as shown in the right hand portionof FIG. 6, and as previously described.

If desired, the wedges as previously described may extend completelyfrom the center 94 of one axially projecting arm 24 to the center 96 ofthe next axially projecting arm 24 as shown in FIG. 8. That is, thedeepest part of the wedge will be along the center 94 of arm 24, andwill taper therefrom to the center 96 of the next arm 24, intersectingthe plane surface of the polygon as illustrated by the dotted lines 98.This arrangement results in a series of alternating alterations orcolumns 18 that are staggered with respect to the center plane of theannulus 16 denoted by line 106. Thus, the longitudinal axes of twoadjacent columns 18 form an angle A at the intersection of the adjacentcolumns 18. Also the axial center plane of each. column 18 crosses line106 at approximately the circumferential midpoint of the column 18 atpoint 110. The angle B between line 106 and 20 preferably does notexceed 45. Arm 24 projects perpendicularly to the plane of the annulus16 as shown by the intersection of the center 94 of arm 24 and line 106.The arms 24 alternately project from thefront and rear faces of each ofthe adjacent columns 18 and, each arm 24 will project from the face ofannulus 16 where the longitudinal axes 94 and 96 the adjacent arms 24 ofthe longitudinal axes 20 of the adjacent columnsl8 intersect to formacute angles C and D.

p The preferred configuration and arrangement of the columns 18 is tohave angle A always obtuse, but it should be understood that it is.possible for angle A to be either an acute angle or a right angle.

' It should be understood that whichever one of the configurations ofthe recesses chosen should be used on all columns, both on the front andrear faces thereof.

In operation, hubs 28 and 30 are placed upon shafts 12 and 14 andsecured thereto in a conventional manner as, for example, by inserting aset screw 38 into the aperture 40 in collar 42 and then tightening theset screw 38 onto shafts 12 and 14. Shafts 12 and 14 are then placed insubstantially coaxially and closely spaced relationship with the amountof end clearance between shafts l2 and 14 as desired. The annulus 16 isthen spread apart at split 51 and placed around the shafts 12 and 14 andinto position so that the arms 24 are mated with the recesses 44 in thehubs 28 and'30. The cap screws 32 are tightened tosecure the arms 24securely in the hubs 28 and 30 and to compress annulus 16. The annulus16 is initially from ID to 20 percent The foregoing has presented anovel coupling whichis readily removed for replacement and repair andwhichis readily inserted in position in the field. The resilientmaterial which forms the annulus of this coupling is under compression;however, the annulus is not placed under compression until it isattached to the hubs as described. Thus, no compressive set is inducedin theannulus as a result of shelf storage. The annulus is split topermit easy installation at the site. The coupling is flexible andresilient. The annuluss geometry has been improved to effectively reducethe axial thrust forces created by the compression of the annulus.

The coupling described above is a polygon of octagonal configuration.Obviously other polygons may be used if desired. The column between thearms may be curved so that'the annulus is or approaches a circularconfiguration, especially in its free state, but the performance of acircular configuration, i.e., one in which the columns are curved ratherthan the straight columns of a polygon, is inferior. The reason isbelieved to be that the columns of a round annulus are subjected toeccentric loading which induces buckling at relatively low stresses.

Accordingly, the invention having been described in its best embodimentand mode of operation, that which is desired to by claimed by LettersPatent is:

lclaim: v 1. A coupling for two generally coaxially aligned shaftscomprising:

an annulus having a series of rectilinear, resilient, and compressiblecolumns connected with their longitudinal axes along the sides of a flatpolygon; an arm means projecting transversely of said longitudinal axesat each intersection of two adjacent columns; I said arm meansalternately projecting from the front and rear faces of each of saidadjacentcolumns with respect to the plane of saidflat polygon; a hubmeans on each of said shafts for receiving alternate ones of said armmeans respectively; and a fastening means operative radially throughsaid arm means forsecuring said arm means to said hub means anddecreasing the radius of said annulus thereby placing the columns undera precompressive'load, said annulus further including: a recess on eachof said front and rear faces of said columns extending from theprojection of said arm.

means toward the opposite end of said columns for reducingaxial thrustforces during compression of said annulus.

2. The coupling of claim 1 wherein said recesses are wedgeshaped'tapering from their deepest points adjacent the projection ofsaid arrn means to the surface of said faces.

3. The coupling of claim 1 wherein the length of said recesses islessthan one-half the length of said columns.

4. The coupling of claim '1 wherein the length of said recesses is morethan one-half the length of said columns. I

5. Thecoupling of claim 1 wherein the length of said recesses issubstantially one-half the length -of said columns.

6. The coupling of claim 2 wherein said wedges are formed atsubstantially identical an'gles'on said front and rear faces of each ofsaid columns to provide said columns with a substantially uniformcross-sectional area with respect to the flat sides of each of saidcolumns.

7. The coupling of claim 1 wherein said recesses on each of said frontand rear faces of said column are forces.

8. The coupling of claim 1 wherein said recesses on each of said frontand rear faces of said column are rectangular in shape for reducing saidaxial thrust.

9. The coupling of claim 1 wherein the width of said recesses is lessthan the radial width of said front and rear faces on said columnthereby forming at least one wall between the edge of said recess and anedge of said column.

10. The coupling of claim 1 wherein the width of said recesses issubstantially equal to the radial width of said front and rear faces ofsaid column.

11. The coupling of claim 2 wherein the angle formed by the intersectionof a top surface of each of said wedges with said faces is substantially6 and the longitudinal length of said wedges is substantially 55 percentof the longitudinal length of said columns.

12. The coupling of claim 1 wherein one of said arm means is splitthereby forming two ends of said annulus which may be separated forplacing said annulus about said shafts.

13. The coupling of claim 1 wherein:

said arm means are integral with said annulus;

said arm means being generally wedge-shaped with the smaller end of saidwedge directed toward the axes of said shafts; and

said hub means having correspondingly wedgeshaped slots adapted toreceive said arm means upon radial compression of said annulus by saidfastening means.

14. The coupling of claim 13 wherein said fastening means comprisesscrew means extending radially through each of said arm means and intosaid slots for securing said arm means to said hub means.

15. An elastomeric annulus for connecting a pair of adjacent hubsattached to two generally coaxiallyaligned shafts, said annulusincluding:

a series of rectilinear, resilient, and compressible columns connectedwith their longitudinal axes along the sides of a flat polygon;

an arm means projecting transversely of said longitudinal axes at eachintersection of two adjacent columns;

said arm means alternately projecting from the front and rear faces ofeach of said adjacent columns with respect to the plane of said flatpolygon; and

a recess on each of said front and rear faces of said columns extendingfrom the projection of said arm means toward the opposite end of saidcolumns.

16. The annulus of claim 15 wherein said recesses are wedge-shapedtapering from their deepest points adjacent the projection of said armmeans to the surface of said faces.

17. The annulus of claim 15 wherein the length of said recesses is lessthan one-half the length of said columns.

18. The annulus of claim 15 wherein the length of said recesses is morethan one-half the length of said columns.

19. The annulus of claim 15 wherein the length of said recesses issubstantially one-half the length of said columns.

20. The annulus of claim 15 wherein said recesses on each of said frontand rear faces of said column are truncated wedge-shaped for reducingsaid axial thrust forces.

21. The annulus of claim 15 wherein said recesses on each of said frontand rear faces of said column are rectangular in shape for reducing saidaxial thrust.

22. The annulus of claim 15 wherein the width of said recesses is lessthan the radial width of said front and rear faces of said columnthereby forming at least one wall between the edge of said recess and anedge of said column.

23. The annulus of claim 15 wherein the width of said recesses issubstantially equal to the radial width of said front and rear faces ofsaid column.

24. The annulus of claim 16 wherein the angle formed by the intersectionof a top surface of each of said wedges with said faces is substantially6 degrees and the longitudinal length of said wedges is substantially 55percent of the longitudinal length of said columns.

25. The annulus of claim 15 wherein one of said arm means is splitthereby forming two ends on said annulus which may be separated forplacing said annulus about said shafts.

26. The annulus of claim 15 wherein:

said arm means are integral with said annulus; and said arm means beinggenerally wedge-shaped with the smaller end of said wedge directedtoward the axes of said shafts.

27. An elastomeric annulus for connecting a pair of adjacent hubsattached to two generally coaxially aligned shafts, said annulusincluding:

a series of resilient and compressible columns connected as alternatingalterations so that the longitudinal axes of two adjacent columns forman angle at the intersection of said adjacent columns;

an arm means projecting perpendicular to the plane of said annulus ateach intersection of said two adjacent columns;

said arm means alternately projecting from the front and rear faces ofeach of said adjacent columns with respect to the plane of said annulus;and

said arm means projecting from each of said faces where the intersectionof the longitudinal axis of said arm and the longitudinal axes of saidadjacent columns form acute angles with respect to each of said adjacentcolumns.

28. The elastomeric annulus of claim 27 wherein said longitudinal axesof said adjacent columns form an acute angle.

29. The elastomeric annulus of claim 27 wherein said longitudinal axesof said adjacent columns form an obtuse angle.

30. The elastomeric annulus of claim 27 wherein said longitudinal axesof said adjacent columns form a right angle.

l l t I I

1. A coupling for two generally coaxially aligned shafts comprising: anannulus having a series of rectilinear, resilient, and compressiblecolumns connected with their longitudinal axes along the sides of a flatpolygon; an arm means projecting transversely of said longitudinal axesat each intersection of two adjacent columns; said arm means alternatelyprojecting from the front and rear faces of each of said adjacentcolumns with respect to the plane of said flat polygon; a hub means oneach of said shafts for receiving alternate ones of said arm meansrespectively; and a fastening means operative radially through said armmeans for securing said arm means to said hub means and decreasing theradius of said annulus thereby placing the columns under aprecompressive load, said annulus further including: a recess on each ofsaid front and rear faces of said columns extending from the projectionof said arm means toward the opposite end of said columns for reducingaxial thrust forces during compression of said annulus.
 2. The couplingof claim 1 wherein said recesses are wedge shaped tapering from theirdeepest points adjacent the projection of said arm means to the surfaceof said faces.
 3. The coupling of claim 1 wherein the length of saidrecesses is less than one-half the length of said columns.
 4. Thecoupling of claim 1 wherein the length of said recesses is more thanone-half the length of said columns.
 5. The coupling of claim 1 whereinthe length of said recesses is substantially one-half the length of saidcolumns.
 6. The coupling of claim 2 wherein said wedges are formed atsubstantially identical angles on said front and rear faces of each ofsaid columns to provide said columns with a substantially uniformcross-sectional area with respect to the flat sides of each of saidcolumns.
 7. The coupling of claim 1 wherein said recesses on each ofsaid front and rear faces of said column are truncated wedge shaped forreducing said axial thrust forces.
 8. The coupling of claim 1 whereinsaid recesses on each of said front and rear faces of said column arerectangular in shape for reducing said axial thrust.
 9. The coupling ofclaim 1 wherein the width of said recesses is less than the radial widthof said front and rear faces on said column thereby forming at least onewall between the edge of said recess and an edge of said column.
 10. Thecoupling of claim 1 wherein the width of said recesses is substantiallyequal to the radial width of said front and rear faces of said column.11. The coupling of claim 2 wherein the angle formed by the intersectionof a top surface of each of said wedges with said faces is substantially6* and the longitudinal length of said wedges is substantially 55percent of the longitudinal length of said columns.
 12. The coupling ofclaim 1 wherein one of said arm means is split thereby forming two endsof said annulus which may be separated for placing said annulus aboutsaid shafts.
 13. The coupling of claim 1 wherein: said arm means areintegral with said annulus; said arm means being generally wedge-shapedwith the smaller end of said wedge directed toward the axes of saidshafts; and said hub means having correspondingly wedge-shaped slotsadapted to receive said arm means upon radial compression of saidannulus by said fastening means.
 14. The coupling of claim 13 whereinsaid fastening means comprises screw means extending radially througheach of said arm means and into said slots for securing said arm meansto said hub means.
 15. An elastomeric annulus for connecting a pair ofadjacent hubs attached to two generally coaxially aligned shafts, saidannulus including: a series of rectilinear, resilient, and compressiblecolumns connected with their longitudinal axes along the sides of a flatpolygon; an arm means projecting transversely of said longitudinal axesat each intersection of two adjacent columns; said arm means alternatelyprojecting from the front and rear faces of each of said adjacentcolumns with respect to the plane of said flat polygon; and a recess oneach of said front and rear faces of said columns extending from theprojection of said arm means toward the opposite end of said columns.16. The annulus of claim 15 wherein said recesses are wedge-shapedtapering from their deepest points adjacent the projection of said armmeans to the surface of said faces.
 17. The annulus of claim 15 whereinthe length of said recesses is less than one-half the length of saidcolumns.
 18. The annulus of claim 15 wherein the length of said recessesis more than one-half the length of said columns.
 19. The annulus ofclaim 15 wherein the length of said recesses is substantially one-halfthe length of said columns.
 20. The annulus of claim 15 wherein saidrecesses on each of said front and rear faces of said column aretruncated wedge-shaped for reducing said axial thrust forces.
 21. Theannulus of claim 15 wherein said recesses on each of said front and rearfaces of said column are rectangular in shape for reducing said axialthrust.
 22. The annulus of claim 15 wherein the width of said recessesis less than the radial width of said front and rear faces of saidcolumn thereby forming at least one wall between the edge of said recessand an edge of said column.
 23. The annulus of claim 15 wherein thewidth of said recesses is substantially equal to the radial width ofsaid front and rear faces of said column.
 24. The annulus of claim 16wherein the angle formed by the intersection of a top surface of each ofsaid wedges with said faces is substantially 6 degrees and thelongitudinal length of said wedges is substantially 55 percent of thelongitudinal length of said columns.
 25. The annulus of claim 15 whereinone of said arm means is split thereby forming two ends on said annuluswhich may be separated for placing said annulus about said shafts. 26.The annulus of claim 15 wherein: said arm means are integral with saidannulus; and said arm means being generally wedge-shaped with thesmaller end of said wedge directed toward the axes of said shafts. 27.An elastomeric annulus for connecting a pair of adjacent hubs attachedto two generally coaxially aligned shafts, said annulus including: aseries of resilient and Compressible columns connected as alternatingalterations so that the longitudinal axes of two adjacent columns forman angle at the intersection of said adjacent columns; an arm meansprojecting perpendicular to the plane of said annulus at eachintersection of said two adjacent columns; said arm means alternatelyprojecting from the front and rear faces of each of said adjacentcolumns with respect to the plane of said annulus; and said arm meansprojecting from each of said faces where the intersection of thelongitudinal axis of said arm and the longitudinal axes of said adjacentcolumns form acute angles with respect to each of said adjacent columns.28. The elastomeric annulus of claim 27 wherein said longitudinal axesof said adjacent columns form an acute angle.
 29. The elastomericannulus of claim 27 wherein said longitudinal axes of said adjacentcolumns form an obtuse angle.
 30. The elastomeric annulus of claim 27wherein said longitudinal axes of said adjacent columns form a rightangle.